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• More than two-thirds of people tip their head to the right when they kiss.

• People exchange between 10 million and 1 billion bacteria when they kiss.

• The film with the most kisses is "Don Juan" (1926) with more than 127 kisses.

• "Splendor in the Grass," with Natalie Wood and Warren Beatty, contains the first on-screen French kiss.

• Kissing at the conclusion of a wedding ceremony can be traced to ancient Roman tradition where a kiss was used to seal contracts.

• In 2005, the longest record for kissing was set in London. The kiss lasted 31 hours, 30 minutes and 30 seconds.

• French kissing involves all 34 muscles in the face. A pucker kiss involves only two.

• It is possible for a woman to reach an orgasm through kissing.

• While kissing releases the stress-reducing hormone cortisol, and burns 2-3 calories per minute, there is a scientific mystery behind the reason our eyes are closed when kissing.

In March, 2016 some actual scientific data solved this mini-mystery.

The research by Dr. Sandra Murphy and Dr. Polly Dalton was published in the Journal of Experimental Psychology: Human Perception and Performance by University of London .

It is important to note that the researchers "did not make a bunch of their test subjects kiss each other in a lab." Participants in the study were asked to pay attention to flashing letters on a screen.

The psychologists "asked participants to carry out visual tasks while seeing if they could detect a brief vibration delivered to their hands at the same time.

We value and respect our HERWriters' experiences, but everyone is different. Many of our writers are speaking from personal experience, and what's worked for them may not work for you. Their articles are not a substitute for medical advice, although we hope you can gain knowledge from their insight.